As technologies further advance, a variety of battery powered portable devices, such as mobile phones, tablet PCs, digital cameras, MP3 players and/or the like, have become popular. Each portable device may employ a plurality of rechargeable battery cells. The plurality of rechargeable battery cells may be connected in series or in parallel so as to form a rechargeable battery pack for storing electrical energy.
According to different combinations of electrode materials and electrolytes used in rechargeable batteries, rechargeable batteries may be divided into a variety of categories. The most common rechargeable batteries include nickel-cadmium (NiCd) batteries, nickel-metal hydride (NiMH) batteries, lithium-ion batteries, lithium-ion polymer batteries, lithium-air batteries, lithium iron phosphate batteries and the like.
As power consumption has become more important, there may be a need for accurately monitoring the charge and discharge currents flowing through a rechargeable battery so as to achieve fast, safe and complete charging of the rechargeable battery. Current mirror based battery monitoring devices have become the preferred choice for achieving high performance (e.g., accurate current measurement information) because current mirrors are capable of generating a replica proportional to the current flowing through the rechargeable battery. However, as the current flowing through the rechargeable battery goes lower, the accuracy of the current mirror has become a significant issue, which presents challenges to designers of battery charger systems.